Crude oil conversion process with coking in the first stage and the subsequent hydrocracking and reforming of the products



3,238,117 RST STAGE W. F. AREY, JR.. ETAL ION PROCESS WITH COKING IN THEF1 AND THE SUBSEQUENT HYDROCRACKING AND REFORMING OF THE PRODUCTS FiledJuly 3, 1965 558mm .8 on N Jon m. mu mm mm; m N N MMWE F 0M1 Q m: N? O mi v. 21 5x8 E w 0 nm3 6 March 1, 1966 CRUDE OIL CONVERS William FloydArey,J Charles Newton Kimberlin, Jr, 'nven'mrs PutenfAflorney UnitedStates Patent CRUDE 01L CONVERSION PROCESS WHTH COK- ING IN THE FIRSTSTAGE AND THE SUBSE- QUENT HYDROCRACKING AND REFORMTNG OF THE PRODUCTSWilliam Floyd Arey, Jr., and Charles Newton Kimberlin, Jr., Baton Rouge,La., assiguors to Esso Research and Engineering Company, a corporationof Delaware Filed July 3, 1963, Ser. No. 292,703 6 Claims. (Cl. 208-53)The present invention relates to a process for converting crudepetroleum oil to desired products by a combination of steps includingcoking, hydrocracking, and reforming. More particularly, the inventionconcerns such a combination process wherein crude oil feed is subjectedto a coking operation, the total liquid product thereby obtained issubjected to a hydrocracking operation, and the heavy naphtha portion ofthe hydrocracked product is subjected to a reforming operation.

In the conversion of petroleum crude oilsto commercial product it isdesirable to obtain a maximum yield of products of high economic valuesuch as gasoline and heating oil and a minimum of products of loweconomic value such as heavy residua. Combination processes whichincrease the production of high octane motor fuels are particularlyvaluable.

In accordance with the present invention, an improved combinationprocess is employed wherein crude petroleum oil is supplied to a cokingzone. For the purposes of this invention, the term crude oil is intendedto embrace not only whole crude petroleum oil but also long residuum ortopped crude, i.e. crude oil from which the lower boiling materials suchas naturally-occurring gasoline or heavy naphtha fractions have beenremoved. Coke and gas are separated from the coker product and theentire liquid portion of the product is then subjected to ahydrocracking operation. After recycle hydrogen gas has been separatedfrom the hydrocracking effluent, the latter is then fed to adistillation zone and separated by distillation into a number of cutsincluding a heavy naphtha fraction having 0; hydrocarbons and higher,one or more fractions including C hydrocarbons and lower, and a bottomsfraction boiling above about 430 F. If a heating oil product is desired,a side stream boiling in the range of 350 to 700 F. may also be takenoff from the distillation zone. Also, it is usually preferred to haveone cut of C to C hydrocarbons which can be blended into motor fuel. Theheavy naphtha fraction obtained in the distillation is sent to areforming zone where it is reformed to give a high octane product underconditions furnishing an excess of hydrogen. The latter is used in thehydrocracking step. With a large number of crude oils the reformingoperation will furnish suflicient hydrogen for the hydrocracking step.However, if additional hydrogen is required it can be manufactured fromthe light gas, i.e. propane and lower.

The operation of the various steps in the combination process of thepresent invention will be better understood when reference is made tothe drawing in which the single figure represents a flow diagram of theprocess. Referring now to the drawing in detail, the reference character10 designates a line for feeding a whole petroleum crude oil, a longresiduum or a topped crude into a coking zone 11. The crude oils whichmay be used include domestic crudes such as South Louisiana, West Texas,Midcontinent, and the like, or Middle East crudes such as Arabian orKuwait.

Coking zone 11 may comprise any of the conventional coking units. Sincethe standard coking processes are well known in the art, it is notconsidered necessary to show the coking process in detail. The unitspresently 3,238,117 Patented Mar. 1, 1966 available for this purpose areof either the delayed coking or fluid coking variety. In a delayedcoker, the feed is heated to about 750 F. to 950 F. and then sent intoone of two or more coking zones which are connected by valves so thatthey may be put on stream for filling and then taken off stream for cokeremoval as the amount of coke formed therein builds up to the maximumcapacity. The temperature in the coking zone is ordinarily in the rangeof about 775 F. to 850 F. and under a pressure of from about 40 to 60p.s.i.g. In the present invention it is preferred to use a fluid type ofcoking unit wherein the feed is sprayed into a chamber for contact withhot particulate solids maintained in a fluidized condition by means ofan upflowing stream of fluidizing gas such as steam or a lighthydrocarbon gas. When the feed contacts the fluidized bed of solids, theoil undergoes pyrolysis, evolving lighter hydrocarbons and depositingcarbonaceous residue on the solid particles, causing them to grow insize. The necessary heat for the pyrolysis is supplied by circulating astream of the fluidized solids through an external heating or combustionzone and then passing the resulting hot coke particles back to thefluidized coking zone for contact with incoming feed. The

vaporous products formed in the fluidized coking chamber are separatedfrom entrained particulate solids through a suitable cyclone type ofseparation unit.

In the present invention, when using a fluid coker operation the cokingstep is carried out at a temperature between about 800 F. and 1200 F.and a pressure between about atmospheric and 15 p.s.i.g. The cokeparticles are of an average size of between about and 1000 microns. Thesuperficial velocity of the upflowing gas and vapor in the coking zoneis between about 0.2 and 5 ft./second, thus maintaining a fluidized bedof coke particles. The circulation rate of coke solids in relation tooil feed is between about 5 and 10. The burner vessel of the coking unitis maintained at a temperature between about 1050" F. and 1600 F.

Coke produced in the process is removed from the coking zone throughline 12. The remaining products of the coking operation, afterseparation from entrained coke particles, are sent through line 13 toseparation zone 14 wherein gas is removed overhead through line 15 andthe total liquid product from the coker is fed by means of line 16 intohydrocracking zone 17. The coker effluent entering zone 14 is cooled toabout P. so that the separation in zone 14 gives a liquid product whichis predominantly C and higher. Thus, most of the C and some C gooverhead with the gas (through line 15) and may subsequently berecovered by known or conventional means. Zone 14 is preferably anintegral part of the coking unit so that the cooling of the cokerefliuent may be accomplished by heat exchange with the crude feed priorto introducing the feed to the coker through line 10. The liquid productleaving zone 14 through line 16 has an initial boiling point of about150 F. and a final boiling point in excess of about 950 F. or higher.

The hydrocracking zone 17 maybe a fixed bed catalyst hydrocracking zoneor it may be a fluid catalyst hydrocracking zone. In either case, withthe present invention it is not necessary to pretreat the feed going tothe hydrocracking zone 17, and hydrocarbon oil feeds containing morethan 50 parts per mill-ion of nitrogen can be tolerated. With veryhigh-nitrogen-containing feeds (above about 500 ppm. nitrogen) a mixedhydrocracking catalyst system is advantageously utilized in a fixed bedhydrocracker. If a fluid hydrocracking zone is used, the catalyst ispreferably one comp-rising between 1 and 15 wt. percent of nickel on asilica-alumina crack-ing catalyst, although other catalysts such ascobalt on silicaalumina or 0.1 to 2 wt. percent of platinum or palladiumon silica-alumina may be used. Particularly preferred is a catalystcomprising from about to 6 wt. percent of nickel on a silica-aluminacracking catalyst containing 70 to 90% silica and to 30% alumina.However, cracking catalysts having higher percentages of alumina may beused if desired. The .temperature in hydrocracking zone 17 when using afluid operation is between about 580 F. and 900 F., preferably about 600F. to 700 F. A reaction pressure of between about 400 and 1800 p.s.i.g.,preferably 500 to 1500 p.s.i.g., is used. Hydrogen gas recycle rates ofbetween about 3,000 and 15,000 cubic feet per barrel of feed, andpreferably about 8,000 to 15,000 cubic feet per barrel of feed, areused. The hydrocarbon feed rate to the hydrocracking zone 17 is betweenabout 0.5 and 5 w./hr./w., preferably between about 1 and 2 w./hr./w.,and the catalyst holding time is in the range of from about 30 minutesand hours, preferably 1 to 3 hours.

If the hydrocracking operation is conducted with a fixed catalyst bed,it is preferred that at least a part of the catalyst base be a molecularsieve, that is, a crystalline zeolite alumino-silicate molecular sievehaving uniform pore openings in the range of from about 6 to 15 A.Particularly desirable catalysts of this type are those having aplatinum group metal or platinum group metal compound deposited on,composited with, or incorporated within a molecular sieve zeolite of 6to 15 A. pore size which has been cationically exchanged to remove amajor proportion, if not all, of its sodium content. Preferably, thesodium content is reduced below 10 wt. percent, based on zeolite. Thepreferred catalyst is palladium on such a molecular sieve base. Platinumgroup metals include platinum, palladium, rhodium, osmium, iridium, andthe like.

Zeolites that have molecular sieve properties are now well known in theart. They include natural zeolites such as faujasite and the syntheticzeolites such as the 13X or 13Y sieves which have effective pore sizesof about 13 A. They also include mordenite which has an effective porediameter of about 9 A.

In general, the anhydrous form of the crystalline molecular sievezeolites that can be composited with platinum group metals and employedin the present invention have chemical formulas that may be expressed interms of moles by the following:

0.0 :l: 0.2Me0 ZAl203.XSiOz In the above formula, Me is selected fromthe group consisting of metal cations and hydrogen, n is the valence ofMe, and X is a number in the range of from about 2.2 to about 14. Mostuseful are those zeolites in which X is in the range from about 3 toabout 6.5. Preferred molecular sieve zeolites for use as hydrocrackingcatalyst bases are those in which the zeolite has been base exchange sothat sodium represents a minor molar proportion of the metal representedas Me.

One way of making the hydrogen form of the sieve is to base exchange itwith an ammonium cation solution and thereafter calcine. The step inwhich the hydrogen form or the NI-l form of the sieve is composited withthe noble metal may be in the nature of a wet impregnation or a baseexchange reaction. Thus a platinum or palladium salt or an ammoniumcomplex of these elements, for instance, Pt(NI-I Cl ammoniumchloroplatinate and many others may be used. The palladium salts such asPdCl may also be used, either for impregnation or base exchange. Theamount of catalytic metal in the finished catalyst is ordinarily between0.01 and about 5.0 weight percent.

A BY molecular sieve may be prepared by mixing 646 grams of water, 157grams of alumina hydrate (65% A1 0 244 grams of sodium hydroxide (97%NaO-H) and 2002 grams of a silica hydrosol and then heat soaking themixture at 210 F. for 4 days. A crystalline product is formed which canbe separated from the mother liquor by filtering and then washed withwater. The product obtained is the sodium form of a 13Y molecular sieve.The sodium form can be converted to the ammonium form by ion exchangewith a solution of ammonium chloride. To prepare a catalyst for a fixedbed hydrocracking operation, the ammonium form of the sieve may beimpregnated with palladium by treating it with a solution of palladiumchloride and converting the impregnated molecular sieve to the activecatalyst by heating to a temperature in the range of 600 F. to 1000" F.to volatilize ammonia and to convert the base to the hydrogen ordecationized form. The amount of palladium in the catalyst may be in therange of 0.01 to 5 wt. percent.

With certain feeds that have high nitrogen contents (above about 500p.p.m.), a mixed catalyst or staged catalyst system may advantageouslybe employed. In such a case, the hydrocracker reactor contains twocatalysts in series. For instance, the inlet portion of the fixed bedmay be made up of a hydrogenation-type catalyst such as cobaltoxide-molybdenum oxide, or nickel oxide-molybdenum oxide, on a base ofeither alumina or silica-alumina. The downstream or outlet portion ofthe bed may consist of a crystalline zeolite catalyst such as palladiumon a hydrogen form of 13Y molecular sieve.

In a fixed bed hydrocracking operation, a temperature of 300 to 900 F.,preferably 500 to 800 tF., is employed and a pressure of 500 to 3000p.s.i.g., preferably 1000 to 2500 p.s.i.g., is used. The hydrogenrecycle rate may range from about 2000 to 30,000, and preferably about3000 to 20,000 cubic feet of hydrogen per barrel of hydro cracking feed.

The product of the hydrocracking treatment is passed by means of line 19into hydrogen separation zone 20 wherein hydrogen is separated from theproduct and recycled to the hydrocracking zone through lines 21 and 18.Associated with zone 20 there may be provided means (not shown) to treatthe separated hydrogen by conventional methods to remove hydrogensulfide and ammonia prior to recycle. After the recycle gas has beenseparated from the hydrocracker effluent the latter is fed by means ofline 23 into a distillation zone 24 wherein conditions are maintained toseparate the material into a number of cuts including a gaseous fractioncomprising propane and lighter gases which are removed through line 25,a C to C fraction which is removed through line 26, a heavy naphthafraction ranging from C hydrocarbons up to an end point of 350 to 430 P.which is removed through line 27, and a bottoms fraction having aboiling point of 350 to 430 F. and higher which is removed through line30 and recycled to the hydrocracking zone 17 through line 16. Ifdesired, a heating oil fraction may be taken as a side stream from thedistillation zone through line 28.

The heavy naphtha fraction in line 27 is sent into a catalytichydroforming zone 31 wherein reforming conditions are maintained thatresult in a net production of hydrogen. Preferably, the catalyst for thehydroforming comprises a fixed bed of a platinum catalyst supported onan alumina support wherein the alumina contains from 0 to 5 wt. percentof silica. The platinum content may range between about 0.01 and 5 wt.percent and preferably the catalyst contains combined halogen in anamount between about 0.3 and 2 wt. percent of fluorine or chlorine orboth.

The temperature maintained in the hydroforming zone is preferably in therange of about 850 F. to 1000" F., the pressure is preferably betweenand 1000 p.s.i.g., and the reaction space velocity is in the range of0.1 to 10 v./hr./v. The amount of hydrogen introduced into zone 31 isusually in the range of about 1000 to 10,000 cubic feet per barrel ofnaphtha feed.

The hydroformed products are passed through line 32 to a liquid-gasseparator 33 for separating hydrogencontaining gas from liquidhydrocarbons. The separating means preferably includes a conventionalabsorption step or the like to remove impurities such as sulfur andnitrogen from the gas. The gas is passed overhead through line 34 and aportion of it is recycled to the hydroforming zone 01 via line 36. Thehydrogen gas produced over and above the quantity recycled to thehydroforming zone is sent by means of line 35 and line 18 to thehydrocracking zone 17. Liquid hydrocarbons separated from the recyclegas in separating zone 33 are withdrawn from the bottom of the separatorby means of line 37 and may be blended into finished gasoline.

While the hydroforming operation has been described as one involving afixed catalyst bed, the hydroforming unit of zone 31 may comprise afluid catalyst reforming zone in which the catalyst employed maycomprise molybdenum trioxide on alumina. Reaction conditions in thiscase include pressures of 50 to 300 p.s.i.g., temperatures of 850 to1000 F., and a feed rate of 0.5 to 2 w./hr./W. with a hydrogenrecirculation rate of 1000 to 5000 standard cubic feet per barrel offeed.

The following is a specific example of the operation of the process ofthis invention. About 10,000 barrels per stream day of whole crudepetroleum oil are introduced by means of line into coking zone 11. Thecrude oil of South Louisiana origin has an API gravity of 38.4 and aConradson carbon content of about 0.8 wt. percent. About 11 tons of cokeand about 9,700 barrels of liquid products having an API gravity ofabout 43 are produced per stream day in coking zone 11. All of this cokeis burned in the regenerator of zone 11 to produce heat for the cokingoperation. With some feeds having a higher Conradson carbon content, anet coke make may result. The temperature in the coking zone is about970 F. and the pressure is about 15 p.s.i.g. The liquid product from thecoking zone has an initial boiling point of about 150 F. and a finalboiling point of about 1000 F.

The fixed bed hydrocracking zone 17 is maintained at a temperature ofabout 680 F. and a pressure of 1500 p.s.i.g. The recycle stream in line18 supplies 10,000 cubic feet of hydrogen per barrel of feed in thehydrocracking step. The catalyst comprises 0.5 wt. percent of palladiumon a hydrogen form of a molecular sieve of about 13 A. The total feed tothe hydrocracker amounts to about 12,700 b./d. being composed of about9,700 b./d. of liquid products from the coker through line 16 and about3,000 b./d. of recycle from the hydrocracker through line 30. Theefiiuent from the hydrocracker 17 passes through line 19 into the highpressure separator 20.

The high pressure separator 20 is maintained at a pressure of about 1500p.s.i.g. and a temperature of about 80 F. The excess hydrogen passesoverhead through line 21 to be recycled to the hydrocracker via line 18.This recycle hydrogen may contain varying amounts of hydrocarbon gases,such as methane. To minimize the build-up of such gases, a small amountof the recycle hydrogen stream is purged via line 22 prior to theintroduction of make-up hydrogen from line 35. About 13,600 barrels perstream day of hydrocarbon liquid product is withdrawn through line 23(and a pressure reducing devicenot shown) into a distillation zone 24which is at about 15 p.s.i.g. pressure. The total product is separatedto give about:

17,000 s.c.f./d. of C gas through line 25 3,300 b./d. of C C hydrocarbonthrough line 26 7,300 b./d. of 180/400 F. naphtha 3,000 b./d. ofhydrocarbons boiling above 400 F.

which are recycled through line 30 to line 16.

In this particular case, no heating oil product is withdrawn as such,although if such a product were desired it could be withdrawn as aseparate side stream through line 28.

About 7300 barrels per stream day of heavy naphtha having a boilingrange between about 180 F. and 400 F. are withdrawn through line 27 ofthe distillation vessel 24 and passed into the hydroforming zone 31which contains a fixed bed of catalyst comprising about 0.5 wt. percentof platinum and 0.2 wt. percent of chlorine on alumina. The hydroformingzone 31 is maintained at a pressure of about 425 p.s.i.g. and atemperature of about 930 F. A liquid space velocity of 1 to 2 v./hr./v.is used. The hydroformed liquid products obtained in line 37 amounts toabout 6000 barrels per stream day when reforming to a product havingResearch octane number (with 3 cc. of tetraethyl lead).

There are a number of advantages gained by employing the process of thepresent invention. The following are particularly noteworthy:

(1) The coking operation removes ash and the metalcontaining compoundsthat occur in crudes and residua. Removal of these components prior tocontacting the oil with a catalyst is highly desirable as thesematerials tend to deactivate the catalyst. Feeding the total crude tothe coker utilizes the coker as a distillation zone, with theundesirable coke product being burned to furnish heat for the process.

(2) Feeding the total liquid product from the coker to the hydrocrackingzone results in stabilizing and desulfurizing the thermal naphtha andheating oil made in the coking operation. Thus, the need for a separateprocessing unit for this purpose is avoided. In addition, the inclusionof the low-boiling material in the feed to hydrocracking improves theoperation of the hydrocracker because the light material increases thedegree of vaporization of the heavy oil. Increased vaporization in ahydrocracker reactor gives improved results, i.e. better catalystactivity and activity maintenance. Also, the low-boiling coker productcontains less nitrogen compounds than does the higher-boiling oil.Inclusion of the light components in the feed to hydrocracking meansthat the nitrogen content of the hydrocracker feed is lower than if thelight components were not included. This is desirable, because theactivity of a hydrocracking catalyst is greater with low nitrogencontent feeds than it is with higher nitrogen content feeds.

(3) In addition to the above, this system of sending the thermal naphthathrough the hydrocracker results in improved volatility of the finalgasoline product.

It will be understood that it is not intended that the scope of thisinvention be limited by the foregoing description of specificembodiments and examples. The true scope of the invention is defined bythe appended claims.

What is claimed is:

1. In a process wherein a feedstock from the class consisting of wholepetroleum crude oils and topped spetroleum crude oils is converted todesired end products by a combination of coking, hydrocracking andreforming steps, the improvement which comprises the steps of subjectingthe entire feedstock to a coking step to form a liquid product boilingin the range between F. and 1000 F. and thereafter subjecting the entiresaid liquid product of the coking step to a hydrocracking step.

2. A process for converting a feedstock from the class consisting ofwhole petroleum crude oils and topped crude oils to desired end productswhich comprises the steps of subjecting the entire feedstock to a cokingstep, to form a liquid product boiling in the range between 150 F. and1000 F., subjecting the entire said liquid product of the coking step tohydrocracking and subjecting the heavy naphtha fraction of thehydrocracked product to a reforming step under conditions resulting in anet production of hydrogen.

3. Process as defined by claim 2 wherein the hydrogen produced in saidreforming step is employed in said hydrocracking step.

4. Process as defined by claim 1 wherein said hydro cracking step isconducted in the presence of a catalyst comprising a molecular sievezeolite impregnated with a platinum group metal.

5. Process as defined by claim 1 wherein said hydrocracking step isconducted in two stages, a hydrogenation catalyst being employed in onestage, and a hydrocracking catalyst being employed in the other stage.

6. In a process for converting a feedstock from the class consisting ofwhole petroleum crude oils and topped petroleum crude oils to desiredend products by a combination of processing steps including coking,hydrocracking and reforming, the improvement which comprises: supplyingthe entire feedstock to a coking zone, subjecting said feedstock tocoking conditions in said zone, including a temperature in the range of8001200 F., separating from the products of said coking zone the entireliquid portion thereof, said entire liquid :portion boiling in the rangebetween 150 F. and 1000 F., subjecting said entire liquid portion tohydrocracking, thereafter separating hydrogen from the hydrocrackedproducts and then distilling the remaining hydrocracked products in adistillation zone into'a number of fractions, including a bottomsfraction boiling above about 300 to 430 F., a heavy naphtha fractionhaving 0; hydrocarbons and higher, and a fraction including Chydrocarbons and lower, recycling said bottoms fraction to thehydrocracking zone, subjecting said heavy naphtha fraction to' areforming step under conditions resulting in a net production ofhydrogen and employing the hydrogen thus produced in said hydrocrackingstep.

References Cited by the Examiner UNITED STATES PATENTS 3,008,895 11/1961Hansford et al 2O8-112 3,072,560 1/1963 Paterson et al. 208- 3.119,7631/1964 Haas et al. 20811O 3,132,090 5/1964 Helfren et al. 208

DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, PAUL E. COUGHLAN,

. Examiners.

2. A PROCESS FOR CONVERTING A FEEDSTOCK FROM THE CLASS CONSISTING OFWHOLE PETROLEUM CRUDE OILS AND TOPPED CRUDE OILS TO DESIRED END PRODUCTSWHICH COMPRISES THE STEPS OF SUBJECTING THE ENTIRE FEEDSTOCK TO A COKINGSTEP, TO FORM A LIQUID PRODUCT BOILING IN THE RANGE BETWEEN 150* F. AND1000*F., SUBJECTING THE ENTIRE SAID LIQUID PRODUCT OF THE COKING STEP TOHYDROCRACKING AND SUBJECTING THE HEAVY NAPHTHA FRACTION OF THEHYDOCRACKED PRODUCT TO A REFORMING STEP UNDER CONDITIONS RESULTING IN ANET PRODUCTION OF HYDROGEN.